Spot blast apparatus



y 3, 1965 R. a. MILLHISER 3,193,975

SPOT BLAST APPARATUS Filed May 1, 1961 2 Sheets-Sheet 1 BY KTM 2 Sheets-Sheet 2 Filed May 1, 1961 INVENTOR Mill/155R United States Patent l r 3,193,975 SPOT BLAST APPARATUS Robert G. Millhiser, 440 Marquette Drive, Detroit 14, Mich. Filed May 1, 1961, Ser. No. 106,931 2 Claims. (Cl. 518) This invention relates to improvements in apparatus for cleaning, polishing, scouring, deburring, and in general abrasive shot blasting and cleaning treatment of parts by liquid blasting. More particularly the present invention relates to apparatus for concentrating such liquid blast, and especially such blast with abrasive granules entrained therein, and directing such concentrated blast against particular areas or in particular directions other than those to which the blast would normally go.

The liquid abrasive blast treatment has been described and claimed in a prior copending application Serial No. 9,910, filed February 19, 1960, now issued as Patent No. 3,150,467. This abrasive blast treatment involves the use of equipment in which abrasive is fed to a short blast tube where it is accelerated by means of high pressure liquid jet or injector near the bottom of the tube which serves to draw abrasive slurry from around the lower entrance of the tube.

As initially practiced, the liquid abrasive blasting was in a vertical direction, the spent blast liquid draining into a tank with a sloping floor and the abrasive grit settling to the bottom of this hopper, where a vertically directed jet tube with injector of high velocity liquid picked up the abrasive slurry and carried it upward in a blast which impinged against an article being held over it. The article can be moved to different positions, and to different orientations to the axis of the blast, so as to expose all necessary areas of the article to the abrasive action. However, it has been found inconvenient and in some cases impossible with a vertical blast to bring all surfaces of each part into the necessary orientation for attaining the desired action.

Especially with parts which have inner chambers or relatively narrow cored passages or bores, the ordinary direct impingement of liquid-suspended abrasive is not capable of hitting all the internal surfaces to smooth a roughened surface or remove projections or sharp edges. Moreover, in practical use, all areas do not require the same degree of blasting treatment. The nature and size of existing flash, burrs or surface imperfections vary from place to place on the surfaces of the articles; especially where there are some surfaces left as cast, whereas adjacent surfaces are machined, it is highly desirable to treat the as-cast surface more severely than the adjacent machined area. On more intricate surfaces and hidden areas, the control of the deburring needs to be not only in degree but also in direction.

We have tried using deflectors of a hardened metal to change the direction of droplets of the blasting slurry from some of the blast jets. As first tried, a hardened metal projection into the blast was used. This had the disadvantage for many uses of spreading the blast stream laterally and thus dissipating to some extent its efiectiveness.

The present invention enables us to deburr or smooth or scour rough surfaces or edges on selected local areas of the parts by better control of the direction of the droplets and abrasive particles of the blast.

The problems with which we are concerned are well illustrated in automobile transmission cases and similar castings having bearing holes and recesses and even orifices for providing oil flow. Care is required in the manufacture of such cases to properly condition the edges of 3,193,975 Patented July 13, 1965 these holesand recesses and the inner surfaces of orifices.

According to our present invention we do this spot deburring, particularly on the internal sections, by mounting the part on a fixture which carries guides that reflect and deflect the droplets of liquid-suspended abrasive being propelled from normal blast tubes. These guides gather the high velocity blast and concentrate the impingement on some, selected area at a proper angle. It is an important advantage of the present invention that it enables us to utilize themost advantageous direction for impingement to smooth rough surfaces or remove sharp edgesand to concentrate abrasive or other blasting material on specific areas. This avoids need for hand deburring which would otherwise be required and gives the desired quality for the assembled part which would otherwise be impaired even by ordinary hand finishing.

In the accompanying drawings I have shown, by way of example, a jig with concentrating guides for use in finishing a standard transmission casting.

In these drawings, FIGURE 1 is a perspective view of a transmission casting mounted in the jig with the various blast nozzles in position.

FIGURE 2 is a diagrammatic plan View of the same.

FIGURE 3 is a side view taken from the right-hand side of FIGURE 2, but with a part of a jig broken away to expose the side of the casting.

FIGURE 4 is a detail view taken on line 4-4 of FIG- URE 3.

Referring to these figures, the casting to be treated is identified by reference character 10. The spot blast fixture 12 is secured to the casting by means of flanges 14 and bolts 16. For this particular casting the fixture is roughly triangular shaped and holds the blast guides 18 accurately positioned with respect to internal openings in the casting or external spots from which roughness, flash or other minor projections are to be removed, and accurately directed to obtain the desired penetration and/or surface action by the abrasive blast.

When the casting with its jig carrying the blast guides is mounted in the blasting machine so that the funnel end of the guide is centered with respect to the abrasive blast, the droplets and granules of abrasive are deflected from the guide tube so as to concentrate the blast axially down into the hole.

For the holes 20 which go through the wall, the guide is positioned coaxial with the holes. With blind holes such as 21, the tube 18 may be coaxial but advantageously is smaller than the hole so that the blast goes down the center, impinges on the bottom of the hole and is reflected back out along the outer faces, producing the desired smoothing of the periphery in the edges of the hole without excessive abrasion of surfaces around the hole. With larger recesses the guide may advantageously be sloped toward the recess so that the exhaust can pass 01f at the far side without interference. Likewise, with areas having flash or surface projections which need to be smoothed down, the guide may be turned to concentrate the blast on such spot and at the most effective angle of incidence for the blast.

It will be obvious that these blast guides are subject to deterioration by abrasion during use; but they are relatively inexpensive in comparison to the accomplishment and the savings achieved and are therefore considered expendible items. In order to minimize such abrasion they are made of a hard, abrasion-resisting material, e.g., high silicon iron castings. Although abrasion can be reduced by using a coating of rubber or the like, this would be expected to slow down abrasive particles by virtue of the yielding impact. However, with the liquid abrasive blasting the liquid tends to provide lubrication to vary the efl' ect so that the yelocity' of the abrasive particles is less impaired than with dry abrasive. 1

I claim:

1. A jig for use in surface treatment of manufactured part-s by'liquid blasting which comprises a frame adapted to'fit around said part, fingerssecured to and extending inwardly from said frame adapted to be secured to said part to hold said frame in fixed precise relation thereto,

' and blast; guideson said frame-haying an open cylindrical inlet tube portion and a conical funnel outlet portion for gathering at least a portion of. ablast and-directing it throughthe funnel portion in aconcentrated blast, said funnel portion forming an acute angle with the internal 7 References Cited by the Examiner UNITED STATES PATENTS 993,743 5/11 Wright 51 11 11,702,203 2/29 Day 51-8 2,007,844 7/35 Baliko' -2 51-8 j 2,138,520 11/38 Elliot a 51-421 2,458,825 1/49 -Baue 518 2,462,480 449 Eppler 51 8 2,505,422, 4/50 Michaels 51- 2, 08,800 9/52 Ritter 51 -319 'FOREIGNPATENTS' j J 961,061 3/57] Germany.

15 LESTER M. SWINGLE, Primary Exaniin er.

FRANKIE. BAILEY, VJOHN c. CHRISTIE, J. SPEN- .CERQVERHOLSER, Examiners. 

1. A JIG FOR USE IN SURFACE TREATMENT OF MANUFACTURED PARTS BY LIQUID BLASTING WHICH COMPRISES A FRAME ADAPTED TO FIT AROUND SAID PART, FINGERS SECURED TO AND EXTENDING INWARDLY FROM SAID FRAME ADAPTED TO BE SECURED TO SAID PART TO HOLD SAID FRAME IN FIXED PRECISE RELATION THERETO, AND BLAST GUIDES ON SAID FRAME HAVING AN OPEN CYLINDRICAL INLET TUBE PORTION AND A CONICAL FUNNEL OUTLET PORTION FOR GATHERING AT LEAST A PORTION OF A BLAST AND DIRECTING IT THROUGH THE FUNNEL PORTION IN A CONCENTRATED BLAST, SAID 